The invention relates to a method and device for winding of fiber webs, especially paper and board webs, into partial web rolls which are wound via a nip between a winding roll and the roll being formed on a winding station from a parent roll.
The invention also relates to a device for winding fiber webs, particularly paper and board webs, into partial web rolls, which device includes a winding station for winding partial web rolls via a nip between a winding roll and the roll being formed.
It is known that a fiber web, e.g. paper, is manufactured in machines which together constitute a paper-manufacturing line which can be hundreds of meters long. Modern paper machines can produce over 450,000 tons of paper per year. The speed of the paper machine can exceed 2,000 m/min and the width of the paper web can be more than 11 meters.
In paper-manufacturing lines, the manufacture of paper takes place as a continuous process. A paper web completed in the paper machine is reeled by a reel-up around a reeling shaft i.e., a reel spool, into a parent roll the diameter of which can be more than 5 meters and the weight more than 160 tons. The purpose of reeling is to modify the paper web manufactured as planar to a more easily processable form. On the reel-up located in the main machine line, the continuous process of the paper machine breaks for the first time and shifts into periodic operation.
The web of parent roll produced in paper manufacture is full-width and even more than 100 km long so it must be slit into partial webs with suitable width and length for the customers of the paper mill. The web from the parent roll is slit and wound around cores into so-called customer rolls before delivering them from the paper mill. This slitting and winding up of the web takes place as known in an appropriate separate machine i.e., a slitter-winder.
On the slitter-winder, the parent roll is unwound, the wide web is slit on the slitting section into several narrower partial webs which are wound up on the winding section around winding cores, such as spools, into customer rolls. When the customer rolls are completed, the slitter-winder is stopped and the rolls i.e. the so-called set is removed from the machine. Then, the process is continued with the winding of a new set. These steps are repeated periodically until paper runs out of the parent roll, whereby a parent roll change is performed and the operation starts again as the unwinding of a new parent roll.
Slitter-winders employ winding devices of different types depending on, inter alia, the type of the fiber web being wound. On slitter-winders of the multistation winder type, the web is guided from the unwinding via guide rolls to the slitting section where the web is slit into partial webs which are further guided to the winding roll/rolls on the winding stations into customer rolls to be wound up onto cores. Adjacent partial webs are wound up on different sides of the winding roll/rolls. Multistation winders have one to three winding rolls and in them each partial web is wound to a partial web roll in its own winding station. During winding a winding nip is formed between the winding roll and the partial web roll to be wound. The winding nip tightens the web in the nip and at a wrap area, that is the area the web runs on the surface of the winding roll. The tightening increases when the winding roll has a soft coating. If the length of the wrap is not long enough, the web will slide on the surface of the winding roll. In case partial webs next to each other have wrap of different length, the result is a difference of tension of partial webs, which causes runnability problems and differences in tightness of the partial web rolls. Attempts have been made in the prior art to solve this by using a tension interruption roll at the winding roll but they have proven unreliable and they also require a lot of maintenance.
Thus when winding up webs on winding stations, it is important that the web stays fast without sliding on the surface of the winding roll when entering the winding nip of the winding station, whereby the tension of the entering web remains in control. If/when sliding in practice occurs, it is important that possible circumferential distances of different lengths of the partial webs i.e. wrap angles of different sizes on the periphery of the winding roll are either eliminated or, if this is not possible, tension differences of the partial webs caused by the surrounding distances of different lengths one may try to compensate by means of the winding technique using different winding parameters. If sliding on different winding stations is different, the partial web rolls are formed different in their hardness.
On some slitters of the multistation winder type known of prior art, the winding up of partial webs occurs on both sides of one winding roll, having the diameter of typically 1,200 mm or 1,500 mm. For instance, specification EP O478719 (U.S. Pat. No. 5,405,099) describes a known winder of a slitter-winder where the winding up of partial webs occurs on both sides of the winding roll and the circumferential distances of partial webs are different on the winding stations positioned on different sides of the winding roll. As a solution for this, patent specification EP O478719 describes the use of a separate so-called tension interruption roll. By the tension interruption roll, the partial webs are locked onto the surface of the winding roll thus aiming to eliminate the effect of sliding. When the web tension provided by the unwinding device is this way interrupted before winding up, the winding up requires additional devices, e.g. center drives of winding stations, which then again provide the web with tension required for winding up. Such a method is not cost-effective in terms of power consumption.
On some other multistation winder types known of prior art, the so-called three-roll winders, which are described e.g. by patent specification F171708 (U.S. Pat. No. 4,601,345) and patent specification U.S. Pat. No. 4,508,283, the winding up of partial webs occurs by means of two winding rolls, typically having the diameter of 850 mm or 1,000 mm, and a guide roll positioned between them. Partial webs are guided separate from each other before guiding to the winding rolls. F171708 describes a winder of a slitter-winder where winding arms are pivoted whereby, as the roll diameter increases, the winding nip transfers on the periphery of the winding roll, i.e. the wrap angle of the web on the winding roll changes. U.S. Pat. No. 4,508,283 describes winders of a slitter-winder where the winding stations are above the winding roll and suspended on a robust cross beam in the cross-machine direction and their support requires massive structures above the winding roll. In these kinds of winders, the roll surrounding distances of partial webs guided on different sides of the winder are optimized such that the distances on the periphery of the winding rolls and the periphery of the guide roll are substantially the same on the winding stations on both sides of the slitter-winder. To ensure uniform winding, the winding rolls and the guide roll are mechanically connected together and this group is driven by one electric motor. The partial web rolls to be wound are supported by arms that move the web roll in relation to the winding roll as the diameter of the partial web roll increases during winding. These kinds of arrangements prerequisites a tight mutual diameter tolerance in the manufacture of winding and guide rolls and support arms of the web rolls, thus making the manufacture of the winder require high precision.
In U.S. Pat. No. 2,460,694 is disclosed a prior art winder with two winding rolls. In this arrangement the partial web rolls to be wound are supported by arms that move the web roll in relation to the winding roll as the diameter of the partial web roll increases during winding and thus the wrap angle changes during winding whereby, as the roll diameter increases, the winding nip transfers on the periphery of the winding roll, i.e. the wrap angle of the web on the winding roll changes.